Integrated circuit memory devices include both volatile and non-volatile memory devices. Volatile memory devices, such as dynamic random access memory (DRAM) devices and static random access memory (SRAM) devices, typically lose data stored therein when power supplies to these memory devices are interrupted. In contrast, non-volatile memory devices are configured to retain stored data even in response to power supply interruptions. Accordingly, non-volatile memory devices are typically suitable for environments where power supply interruptions are frequent.
One type of non-volatile memory device includes a flash memory device, which may utilize NAND-type strings of electrically-erasable programmable read-only memory (EEPROM) cells therein. Typical EEPROM cells include floating-gate type cells and charge-trap type cells, which may utilize a combination of charge storage and charge trapping layers therein. Conventional techniques to achieve high levels of data storage include vertical integration techniques. Some of these techniques are disclosed in US 2007/0252201 to Kito et al., entitled “Nonvolatile Semiconductor Memory Device and Manufacturing Method Thereof,” and US 2007/0158736 to Arai et al., entitled “Semiconductor Memory Device and Method of Fabricating the Same.”